Steering sub for underwater drilling apparatus

ABSTRACT

A tubular steering sub, connected adjacent a drill bit at the bottom of a drill string, steers the bit into alignment with an underwater well. The steering sub comprises an inner barrel splined to an outer barrel to permit axial relative movement between the barrels so that laterally disposed jet ports of the inner barrel and the outer barrel move in and out of alignment. When the jet ports are aligned, a lateral steering force on the bottom of the drill string is generated by pumping fluid down the drill string and out the jet ports. A releasable spring latch closes the steering sub by securing the barrels in fixed relation with their jet ports out of alignment.

United States Patent Norton 51 Mar. 7, 1972 [54] STEERING SUB FOR UNDERWATER 3,315,747 4/1967 Farley etal. "166/226 x DRILLING APPARATUS 3,529,428 9/1970 Batten ..l66/226X Inventor: Thomas R. Norton, Placentia, Calif.

Assignee: Global Marine Inc., Los Angeles, Calif.

Filed: Jan. 9, 1970 Appl. No.: 1,736

References Cited UNITED STATES PATENTS Primary Examiner-Marvin A. Champion Assistant ExaminerRichard E. Favreau Attorney-Christie, Parker & Hale [57] ABSTRACT A tubular steering sub, connected adjacent a drill bit at the bottom of a drill string, steers the bit into alignment with an underwater well. The steering sub comprises an inner barrel splined to an outer barrel to permit axial relative movement between the barrels so that laterally disposed jet ports of the inner barrel and the outer barrel move in and out of alignment. When the jet ports are aligned, a lateral steering force on the bottom of the drill string is generated by pumping fluid down the drill string and out the jet ports. A releasable spring latch closes the steering sub by securing the barrels in fixed relation with their jet ports out of alignment.

16 Claims, 3 Drawing Figures PATENTEDMAR 7 I972 SHEET 2 [IF 2 W IQ STEERING SUB FOR UNDERWATER DRILLING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to underwater drilling apparatus, and more particularly to a steering sub located near the bottom of a drill string for steering a drill bit into contact with an underwater location such as a well or the like.

2. Description of the Prior Art During underwater well drilling operations, a length of drill string is lowered from a floating vessel to an underwater formation and a drill bit at the bottom of the drill string drills a well in the formation. During drilling, contact between the bit and the well is often interrupted, and as a result, a substantial amount of drilling time may be required to realign the drill bit with the well hole. These realignment procedures are time consuming because the large inertia of the long drill string makes it difficult to accurately steer the drill bit in substantial depths of water. The steering problem is further compounded by wave action which causes the floating vessel to move relative to the well.

In the past, the problems associated with steering a drill string into alignment with a well have been relieved somewhat by the use of steering mechanisms attached to the drill string for producing lateral forces adjacent to its lower end. Some steering mechanisms have motor-driven propellers and the like mounted near the bottom of the drill string. Other steering mechanisms comprise special attachments mounted outboard of the drill string for producing water jets or .the like to propel the bottom of the drill string laterally through the water. These prior art devices have not been particularly satisfactory because they are relatively expensive to construct and because they contribute substantial additional weight to the drillstring; also, and perhaps more importantly, they hinder reentry of the drill string into the hole once proper alignment has been achieved. Construction costs and weight are increased by the jettype steering devices which ordinarily require the use of auxiliary conduits and valve apparatus. Furthermore, the previous steering device structuresare ordinarily spaced outboard of the drill string, with the result that theinertia of the drill string lower end is increased, thereby'making it more difficult to move the drill string laterally through the water.

Realignment problems are greatest in the .early stages of drilling a well. Once a wellhead landing base-has been placed,

guide cables between the base and the vessel makeit possible to guide the drill string to the well hole. Reentry is also a considerable problem in coring for bottom samples. No landing bases are used in conventional coring operations and reentry using conventional steering devices is extremely difficult.

SUMMARY OF THE INVENTION This invention contemplates a drill stringsubunit adapted for steering the lower end of the-string into alignment with a well hole. The subunit, hereinafter referred to as a steering sub, produces lateral steering forces for-the lower end of the drill string without the use of expensive auxiliary steering mechanisms such as motor-driven propellers. The steering sub is relatively small in size and is'simple in construction. As a result, it is substantially less expensive and lighter'in weight than previous steering devices. Further, the steering sub is an integral part of the drill string and contains no structural components disposed outboard of the drill string. Thus, the inertia of the drill string base is not perceptibly increased, and no auxiliary conduits or valve apparatus are required. Moreover, the steering sub does not hinder reentry of the drill string into the hole once proper alignment has been achieved. Thus, the realignment problems associated with coring operations and with the early stages of well drilling operations are substantially avoided.

Briefly, the steering sub apparatus includes an outer barrel, a hollow inner barrel inside the outer barrel arranged to move axially relative to the outer barrel between a first position and a second position. Releasable latching means normally maintain the inner barrel and the outer barrel in their first relative position, and means for releasing the latching means is operative to permit relative movement of the barrels to the second relative position. In the second relative position, the inner barre] and the outer barrel define alateral fluid flow passage through the barrels. In use, pressurized fluid flowing to the interior of the inner barrel is expelled through the lateral fluid flow passage to the body of water externally of the outer barrel to thereby exert a reactive lateral steering force on the sub and the portion of a drill string in which the sub is incorporated in use.

In the preferred form of the invention, the releasable latching means comprises a spring biased into engagement with cooperatively arranged keeper means for latching engagement between the inner barrel and the outer barrel in the first relative position of the barrels. Preferably, the means for releasing the latching means includes pressure responsive means such as a piston arranged for movement between a first tion as the drill string is lowered from the floating vessel to the underwater formation. Thus, lateral steering forces are applied adjacent to the lower end of the drill string as desired by pumping fluid down the drill string and out the lateral flow passage. Once the drill string has entered the well, the steering submay be closed by applying weight on the drill bit to move the inner barrel and the outer'barrel relative to each other until they reach the first relative position where the keeper means secures the barrels together and closes the lateral flow passage. If it later becomes necessary to realign the drill bit with the well, the steering sub may be opened by moving the movable element of the latch releasing means to its second position to release the keeper means from latching engagement with the barrels, thereby permitting the barrels to move to the second relative position so that fluid can be ejected from'the lateral flow passage.

BRIEF DESCRIPTIONOF THE-DRAWINGS DETAILED DESCRIPTION OF A SPECIFIC EMBODIMENT Referring'to the drawing, FIG. .1 shows-awell l0'being drilled in an underwater formation 12 from a drilling vessel 14 floating on a body of water .I6.-An upright, elongated hollow .drill string 18 extends downwardly from vessel 14. through the body of :water to .well I0. A rotary drill bit 20 on the lower end of drill stringl-8 drills well l0. An upper section 22 of drill 'string-l8is supported in a cellar.24 which opens centrally through drilling'vessell4. A conventional rotary table 26 is mounted directly over cellar 24. 'An elongated, hollow kelly joint 28 cooperates with a kelly bushing (not shown) in the center of the rotary table so that rotary motion of the bushing is transferred to the kelly joint, thereby to rotate drill string 18, and drill bit 20, which is connected to the lower end of the kelly joint in the conventional manner. The kelly joint 28 is coupled at its top to a swivel 30 supported by a travelling block 32 suspended from a stationary crown block 34 at the top ofa derrick 36 mounted on the deck of floating vessel 14.

During use of the drilling apparatus shown in FIG. 1, drill string 18 and drill bit are lowered from floating vessel 14 to underwater formation 12. A locating device 38, such as a TV camera or a sonar device, mounted near the bottom of drill string 18 by support 40, permits viewing of the desired well site as the drill string is lowered. A tubular steering sub 42 of this invention is connected in drill string 18 essentially directly above drill bit 20 to provide alignment of the drill bit with the desired well site. As drill string 18 is lowered, steering sub 42 is maintained in an open condition to exert a reactive lateral steering force on the bottom of the drill string by directing a jet of fluid 46 laterally outwardly from its side. After drill bit 20 is located at the desired well site, steering sub 42 is closed by a latching device 70 (see FlGS. 2 and 3) hereinafter described, and drilling operations proceed in the conventional manner by rotating drill string 18 and drill bit 20 with rotary table 26 to drill well 10. In the event contact between the drill bit and the well is later interrupted, either deliberately or inadvertently, steering sub 42 is opened without the necessity of completely retracting drill string 18 to the vessel; this is done by using latching device 70 (see FIG. 3) in a manner hereinafter described. With the steering sub 42 in its open position, a steering jet 46 is produced to exert a lateral force on the bottom of drill string 18 to realign drill bit 20 with well 10. The direction of the steeringjet relative to the drill string is controlled by suitably adjusting the angular position of the drill string using rotary table 26.

During drilling, a supply of drilling mud 48 is delivered from a tank 50 aboard floating vessel 14 to a flexible mud supply line 52 by a pump 54 and a drawoff pipe 56 connected to the pump intake port. Supply line 52 extends upwardly to connect with swivel 32. During operation of pump 54, under normal circumstances, drilling mud travels through supply line 52, through swivel 32, down the interior of kellyjoint 28 and drill string 18, through closed steering sub 42, and out drill bit 20 to clean the bit of cuttings produced by operation of the bit. When steering sub 42 is in its open condition, steeringjet 46 is produced by pumping the drilling mud down the drill string and forcing it out through the side of steering sub 42 in a manner hereinafter described.

The construction and operation of steering sub 42 is best understood by referring to FIG. 2 which shows the steering sub in its closed condition. The steering sub includes an elongated outer barrel 58 and an elongated inner barrel 60 concentrically aligned with the outer barrel. The inner barrel is splined at 80 to the outer barrel to allow the barrels to move axially but not angularly relative to each other.

Outer barrel 58 defines at its top an externally threaded sec tion 62 adapted for engagement with a conventional internally threaded section 64 at the bottom of drill string upper section 22. Outer barrel 58 extends downwardly away from drill string upper section 22 to define a laterally disposed outer jet port 66 formed through its sidewall and an inwardly projecting annular shoulder 68 formed in its interior wall a short distance below outer jet port 66. Preferably three latching devices 70, hereinafter described in detail are uniformly spaced around the bottom ofouter barrel 58 for use in fastening the inner and outer barrels in their closed condition shown in FIG. 2.

Inner barrel 60 defines, near its top, a laterally disposed innerjet port 72 extending through its sidewall. A fluid-sealing upper O-ring 74 is seated in the outer sidewall of the inner barrel above innerjet port 72, and a fluid-sealing lower O-ring 76 is seated in the outer sidewall of the barrel below innerjet port 72. When steering sub 42 is in its closed condition, inner jet port 72 is out of alignment with outerjet port 66 at a point above lower O-ring 76, as shown in FIG. 2, and is sealed from communication with the outer jet port by O-rings 74 and 76. Inner barrel 60 extends downwardly from innerjet port 72 to define an outwardly projecting annular shoulder 78 in its exterior wall, which shoulder is spaced above annular shoulder 68 of outer barrel 58 when the barrels are closed as shown. An elongated axial spline 80 is defined by the outer sidewall of inner barrel 60 and the inner sidewall ofouter barrel 58 below shoulders 78 and 68 respectively. Spline 80 permits relative longitudinal movement of outer barrel 58 and inner barrel 60 between a first relative position, i.e., the closed position shown in FIG. 2, and a second relative position, i.e., an open position (not shown) where shoulder 78 abuts against shoulder 68. When the barrels are in their open position, innerjet port 72 is aligned withjet port 66. Inner barrel 60 defines, at its bottom, an enlarged lower sleeve section 86 which provides an annular shoulder 88 extending to an inner barrel exterior sidewall 89 having the same diameter as outer barrel 58. Annular shoulder 88 cooperates with an annular end surface 90 of outer barrel 58 to define the closed position of the inner barrel relative to the outer barrel. An O-ring 92 is seated in surface 90 to provide a leakproof seal between the barrels at the lower end of steering sub 42. Inner barrel sleeve section 86 has an internally threaded lower section 94 adapted for engagement with an externally threaded section 96 at the top of drill string lower section 44.

Each latching device 70 is identical in structure and includes a resilient, downwardly extending elongated leaf spring 98 secured at its upper end to a vertically disposed shoulder 100 defined at the upper end ofa recess notch 102 formed in the interior wall of outer barrel 58 near its lower end. When barrels 58 and 60 are closed, recess notch 102 provides space for permitting lateral deflection of leaf spring 98. Latching device 70 further includes a laterally disposed passage 106 extending through inner barrel 60 for communication with recess 102. Passage 106 defines a relatively narrow keeper bore 108 spaced slightly above lateral annular shoulder 88 and extending laterally inwardly from recess 102 where it opens into an enlarged bore 110 concentric to bore 108 and communicating with the interior of inner barrel 60. Leaf spring 98 is normally biased inwardly toward inner barrel 60 so that a keeper catch 112 or lug, mounted to the lower end of the leaf spring, is biased into cooperative engagement with keeper bore 108 normally to maintain outer barrel 58 and inner barrel 60 in the closed condition shown in FIGS. 2 and 3.

Each latching device 70 further includes latch releasing means preferably in the form of a high-pressure spring override element 114 disposed within enlarged bore 110. Element 114 includes a piston 116 movable within bore 110 and a relatively narrow elongated stem 118 extending from piston 116 into cooperative engagement with keeper bore 108. Leaf spring 98 is biased inwardly so that the inner surface of catch 112 normally maintains piston 116 resting against a a retaining ring 120 disposed about the periphery of bore 110 at its opening into the interior of inner barrel 60. An O-ring seal 122 is seated in the outer rim of piston 116 to maintain a leakproof seal between the piston and the walls of bore 110 as the piston slides back and forth in bore 110.

As previously described, during use steering sub 42 is maintained in its open position as drill string 18 is initially lowered to underwater formation 12. The steering sub is opened by initially releasing each leaf spring catch 112 from engagement with its respective keeper bore 108. This allows inner barrel 60 to slide downwardly along outer barrel 58 in the direction of the arrow in FlG. 3 so that shoulder 78 abuts against shoulder 68 to align jet port 72 with jet port 66, as previously described. The steering sub normally maintains its open position as it is lowered to underwater formation 12 because inner barrel 60 is normally subjected to downwardly acting forces resulting from the weight of drill bit 20 and such drill collars as may be connected between the sub and the drill bit. Thus, lateral steering forces can be generated as the drill string is lowered merely by pumping drilling mud down the hollow interior of the drill string. The drill bit 20 is normally structured so that it presents resistance to flow of mud through it, and thus drilling mud pumped down the drill string is forced out wardly through the aligned jet ports 66 and 72 to produce the steering jet 46 for use in maneuvering drill bit 20 into alignment with the desired well site. As previously described, the

direction of the steering jet is controlled using rotary table 26 to rotate drill string 18 to the desired angular orientation.

When the well site is reached, the jet ports 72 and 66 are taken out of alignment by closing steering sub 42. The steering sub is preferably closed by forcing drill string 18 downwardly against formation 12 to apply weight on drill bit 20. This drives inner barrel 60 upwardly relative to outer barrel 58 until keeper catches 112 snap into engagement with keeper bores 108 to thereby secure steering sub 42 in its closed condition shown in FIGS. 2 and 3.

During use, if it becomes necessary to reopen steering sub 42, as in the case where contact between drill bit 20 and well is interrupted, such opening can be accomplished without completely retracting the drill string to drilling vessel 14. Opening of the steering sub is initiated by operating pump 54 at such a level that the fluid passages through drill bit are overwhelmed, thereby to build up high pressure levels in drill string 18. When fluid pressure in the drill string reaches a level greater than the pressure resulting from the forces exerted by leaf springs 98 on high-pressure spring override elements 114, the elements slide outwardly within bores 110 in the direction of the arrows shown in FIG. 3. This lateral movement of elements 114 causes keeper catches 112 to release engagement with keeper bores 108, thereby allowing inner barrel 60 to slide downwardly relative to outer barrel 58 in response to the action of the'weight applied to the inner barrel and the mud pressure within the sub. As previously described, when inner barrel 60 is released from engagement with outer barrel 58, steering sub 42 normally assumes its open position with jet ports 66 and 72 in alignment. In this position, fluid under pressure in the steering sub flows out through the jet ports to produce a lateral force near the bottom of drill string 18 to maneuver drill bit 20 back into alignment with well 10.

The present invention has been described with reference to the specific structure of the best mode presently contemplated for carrying out the invention. lt is to be understood that the scope of the invention is not to be limited to the details of this structure. For example, it can be seen that the structure of steering sub 42 can be altered without departing from the scope of this invention by merely rearranging the barrels to provide an outer barrel structure connected to drill bit 20 and adapted for movement relative to a stationary inner barrel structure connected to drill string upper section 22. It is to be further understood that the particular form of latching device 70 is preferred, and that other releasable locking means for securing the barrels in either an open or a closed position can be used without deviating from the scope of this invention. Furthermore, other means for automatically opening latching device 70 can be used. For example, a ball or the like can be dropped down the hollow interior of drill string 18 to engage a detent or the like extending into the hollow interior of steering sub 42 to release leaf springs 98.

lclaim:

l. A sub for use in association with oil and gas wells and the like, the sub comprising:

a. an outer barrel;

b. a hollow inner barrel inside the outer barrel and movable axially relative to the outer barrel between a first position and a second position;

c. releasable latching means normally operative to maintain the inner barrel and the outer barrel in their first'relative position;

. means responsive to fluid pressure within the inner barrel for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position; and

e. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels.

2. Apparatus according to claim 1 wherein the outer barrel defines one end of the steering sub and the inner barrel defines the other end ofthe steering sub.

3. Apparatus according to claim lincluding means coupling the inner and outer barrels for only axial relative movement.

4. Apparatus according to claim 1 wherein the sub is adapted for connection in a drill string.

5. Apparatus according to claim 4 wherein the outer barrel is adapted for coupling with the upper portion of the drill string and the inner barrel is adapted for coupling with the lower portion of the drill string.

6. Apparatus according to claim 5 wherein the outer barrel has substantially the same diameter as the drill string.

7. Apparatus according to claim 1 wherein the latching means includes a keeper, lug cooperating between the inner and outer barrels, and spring-biasing means cooperating with the keeper lug to maintain the barrels in their first relative position.

8. Apparatus according to claim 7 wherein the spring-biasing means maintains keeper lug cooperatively engaged with a keeper bore disposed in the inner barrel; and wherein the latch release means includes a piston adapted for engagement with the keeper lug, the piston being movable within the keeper bore in response to fluid pressure in the inner barrel to urge the keeper lug out of engagement with the keeper bore to permit relative movement of the inner and outer barrels.

9. A method for aligning with a desired location on the bottom of a body of water the lower end of a drill string pendulously supported from a drilling vessel or the like floating on the body of water, the method comprising the steps of:

a. providing in the drill string adjacent to the lower end thereof a hollow, axially extensible steering sub having a foreshortened first operative condition and an extended second operative condition and defining in the second operative condition thereof a fluid flow passage laterally therethrough from the interior of the drill string to said body of water, and including means effective in the first operative condition to maintain the sub in the first operative condition and responsive to the existence of fluid pressure within the drill string in excess of a predetermined pressure for enabling the 'sub to move from its first to its second operative condition; disposing the sub in its second operative condition; and

c. moving the lower end of the drill string into the desired alignment by applying fluid under pressure to the drill string when the sub is in its second operative condition, thereby to produce a reactive fluid jet force laterally effective on the drill string, and adjusting the effective direction of the force by adjusting the angular position of the drill string.

10. The method according to claim 9 including adjusting the sub from its second to its first operative condition by at least partially supporting the weight of the drill string on the lower end thereof when the pressure of any fluid in the drill string at the sub is less than said predetermined pressure.

11. The method according to claim 9 wherein the sub is adjusted from its first to its second operative condition by disposing the drill string out of supportive engagement with the bottom of said body of water and producing within the drill string at the sub a fluid pressure in excess of said predetermined pressure.

12. The method according to claim 11 wherein the drill string terminates at its lower end'in a rotary drill'bit, and said excess fluid pressure is produced by pumping fluid down the drill string from the vessel at a rate in excess of the maximum rate at which the drill bit canpass such fluid therethrough.

13. A sub for use in association with oil and gas-wells and the like, the sub comprising:

a. an outerbarrel adapted for coupling with an upper portion of a drill string;

a hollow inner barrel inside the outer barrel and movable axially relative to the outer barrel between a first position and a second position, the inner barrel being adapted for coupling with a lower portion ofthe drill string;

c. releasable latching means normally operative to maintain the inner barrel and the outer barrel in their first relative position;

. means for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position; and

. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels.

14. Apparatus according to claim 13 wherein the outer barrel has substantially the same diameter as the drill string.

15. A sub for use in association with oil and gas wells and the like, the sub comprising:

an outer barrel;

a hollow inner barrel inside the outer barrel and coupled for only axial movement relative to the outer barrel between a first position and a second position;

. releasable latching means normally operative to maintain the inner barrel and the outer barrel in their first relative position;

means for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position; and

. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels.

16. A sub for use in association with oil and gas wells and the like, the sub comprising:

a. an outer barrel; b. a hollow inner barrel inside the outer barrel and movable means for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position, the latch release means including a piston adapted to engagement with the keeper lug, the piston being movable within the keeper bore in response to fluid pressure in the inner barrel to urge the keeper lug out of engagement with the keeper bore to permit relative movement of the inner and outer barrels; and

. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position ofthe barrels. 

1. A sub for use in association with oil and gas wells and the like, the sub comprising: a. an outer barrel; b. a hollow inner barrel inside the outer barrel and movable axially relative to the outer barrel between a first position and a second position; c. releasable latching means normally operative to maintain the inner barrel and the outer barrel in their first relative position; d. means responsive to fluid pressure within the inner barrel for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position; and e. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels.
 2. Apparatus according to claim 1 wherein the outer barrel defines one end of the steering sub and the inner barrel defines the other end of the steering sub.
 3. Apparatus according to claim 1 including means coupling the inner and outer barrels for only axial relative movement.
 4. Apparatus according to claim 1 wherein the sub is adapted for connection in a drill string.
 5. Apparatus according to claim 4 wherein the outer barrel is adapted for coupling with the upper portion of the drill string and the inner barrel is adapted for coupling with the lower portion of the drill string.
 6. Apparatus according to claim 5 wherein the outer barrel has substantially the same diameter as the drill string.
 7. Apparatus according to claim 1 wherein the latching means includes a keeper lug cooperating between the inner and outer barrels, and spring-biasing means cooperating with the keeper lug to maintain the barrels in their first relative position.
 8. Apparatus according to claim 7 wherein the spring-biasing means maintains keeper lug cooperatively engaged with a keeper bore disposed in the inner barrel; and wherein the latch release means includes a piston adapted for engagement with the keeper lug, the piston being movable within the keeper bore in response to fluid pressure in the inner barrel to urge the keeper lug out of engagement with the keeper bore to permit relative movement of the inner and outer barrels.
 9. A method for aligning with a desired location on the bottom of a body of water the lower end of a drill string pendulously supported from a drilling vessel or the like floating on the body of water, the method comprising the steps of: a. providing in the drill string adjacent to the lower end thereof a hollow, axially extensible steering sub having a foreshortened first operative condition and an extended second operative condition and defining in the second operative condition thereof a fluid flow passage laterally therethrough from the interior of the drill string to said body of water, and including means effective in the first operative condition to maintain the sub in the first operative condition and responsive to the existence of fluid pressure within the drill string in excess of a predetermined pressure for enabling the sub to move from its first to its second operative condition; b. disposing the sub in its second operative condition; and c. moving the lower end of the drill string into the desired alignment by applying fluid under pressure to the drill string when the sub is in its second operative condition, thereby to produce a reactive fluid jet force laterally effective on the drill string, and adjusting the effective direction of the force by adjusting the angular position of the drill string.
 10. The method according to claim 9 including adjusting the sub from its second to its first operative condition by at least partially supporting the weight of the drill string on the lower end thereof when the pressure of any fluid in the drill string at the sub is less than said predetermined pressure.
 11. The method according to claim 9 wherein the sub is adjusted from its first to its second operative condition by disposing the drill string out of supportive engagement with the bottom of said body of water and producing within the drill string at the sub a fluid pressure in excess of said predetermined pressure.
 12. The method according to claim 11 wherein the drill string terminates at its lower end in a rotary drill bit, and said excess fluid pressure is produced by pumping fluid down the drill string from the vessel at a rate in excess of the maximum rate at which the drill bit can pass such fluid therethrough.
 13. A sub for use in association with oil and gas wells and the like, the sub comprising: a. an outer barrel adapted for coupling with an upper portion of a drill string; b. a hollow inner barrel inside the outer barrel and movable axially relative to the outer barrel between a first position and a second position, the inner barrel being adapted for coupling with a lower portion of the drill string; c. releasable latching means normally operative to maintain the inner barrel and the outer barrel in their first relative position; d. means for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position; and e. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels.
 14. Apparatus according to claim 13 wherein the outer barrel has substantially the same diameter as the drill string.
 15. A sub for use in association with oil and gas wells and the like, the sub comprising: a. an outer barrel; b. a hollow inner barrel inside the outer barrel and coupled for only axial movement relative to the outer barrel between a first position and a second position; c. releasable latching means normally operative to maintain the inner barrel and the outer barrel in their first relative position; d. means for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position; and e. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels.
 16. A sub for use in association with oil and gas wells and the like, the sub comprising: a. an outer barrel; b. a hollow inner barrel inside the outer barrel and movable axially relative to the outer barrel between a first position and a second position; c. releasable latching means including a keeper lug cooperating between the inner and outer barrels, and spring biasing means to maintain the keeper lug cooperatively engaged with a keeper bore disposed in the inner barrel to maintain the barrels in their first relative position; d. means for releasing the latching means to permit relative movement of the inner and outer barrels to their second relative position, the latch release means including a piston adapted to engagement with the keeper lug, the piston being movable within the keeper bore in response to fluid pressure in the inner barrel to urge the keeper lug out of engagement with the keeper bore to permit relative movement of the inner and outer barrels; and e. means cooperating between the inner and outer barrels for defining a lateral fluid flow passage through the barrels only in the second relative position of the barrels. 